A tunnel kiln makes it possible to fire large quantities of refractory ware by a continuous process instead of a batch process. The refractory ware is conveyed through the kiln on kiln cars. The chassis, wheels, and platform of kiln cars are made of metal. The kiln cars are mounted on a track system.
The heat within a refractory kiln is much greater than metals can withstand. The basic problem with kiln cars is how to insulate them from the intense heat within the kiln. Originally, this problem was solved by cementing together small blocks of refractory material on top of the kiln car.
There are several problems with this original solution. For example, when the blocks are exposed to the heat of the kiln, they expand. The cracks between the blocks also expand. Then the cement between the blocks and other debris falls down into the cracks. When the blocks emerge from the kiln and cool, they contract, but they cannot close the cracks because of the debris. After several kiln cycles, the refractory portion of the car must be rebuilt.
Dressler, U.S. Pat. No. 1,521,216, discloses large and massive refractory blocks instead of the smaller blocks that had previously been used. The larger blocks do not need to be cemented together because they are large enough to stay in place. Furthermore, the blocks are interlocking to maintain the blocks in lateral position as the kiln car moves along the track. The vertical cracks between a layer of lower blocks are covered with an overlapping layer of upper blocks. Finally, Dressler '216 teaches forming the blocks with small Cavities. The cavities may be filled with insulating material.
Since the Dressler '216 patent, the price of energy has increased tremendously. Heating these massive blocks of refractory material is a major source of heat loss. The kiln car must be cooled before it can be handled. It requires costly production time for massive refractory members to cool.
Barsby, U.S. Pat. No. 3,759,661, discloses a low thermal mass kiln car. The platform of the kiln car has a plurality of metal sockets. Thin walled refractory posts are removably inserted into the sockets. The posts support refractory tiles that provide an upper surface for placing the refractory ware. The load of refractory ware is supported by the plurality of thin walled refractory posts. The kiln car is insulated from the heat of the kiln by layers of low thermal mass insulation. The insulation is positioned so that the refractory posts may pass through the layers of low thermal mass insulation. The insulation layers are totally non-load-bearing. Furthermore, the insulation does not provide any lateral support to the posts.
Foster, U.S. Pat. No. 4,462,798, discloses a system of triangularly arranged posts for supporting refractory tiles in a stacked and spaced relationship. The tiles provide several stacked surfaces for placing refractory ware. A solid flat refractory base is laid over the platform of the kiln car. Massive pyramid shaped blocks (15.increment..times.15.increment. base, 11.increment. high) of solid refractory material are firmly cemented onto the refractory base such that the apexes of the blocks are arranged in a fixed triangular pattern. The space between the bases of the pyramid blocks to the tops of the pyramid blocks is completely filled with a refractory cement to ensure that the blocks cannot move. In other words, the pyramid blocks are almost completely covered with refractory cement. This forms a high thermal mass refractory base. Each pyramid block has a deep vertical socket (8.increment.) through the apex of the block for receiving a thin walled support post. Foster '798 teaches that the system of posts must be rigidly interconnected to compensate for the movements of the kiln car. The tops of the posts are interconnected to hold them in firmly fixed relation.
Fitz, U.S. Pat. No. 4,721,459, discloses low thermal mass refractory kiln car furniture members. The hollow members are employed to confine low-mass insulation material onto the surface of the kiln car. They are arranged in parallel rows along the perimeter of the rectangular surface of the kiln car. The furniture members thereby define a rectangular volume having a base area almost as great as the surface platform of the kiln car and several inches high. The refractory members are modular. Only a few furniture members must be specifically tooled for a given size kiln car. Insulation material is placed inside the rectangular volume within the perimeter of the furniture members. Insulation is also placed inside the hollow refractory members. Sockets are formed in the platform of the kiln car so that refractory support posts may be removably received therein. The hollow refractory furniture members have holes in the tops so that the refractory support posts may pass therethrough to the sockets in the platform of the kiln car. The refractory furniture members are non-load bearing.
There are several problems with the prior art solutions to the problem of insulating the kiln car from the heat of the kiln. First, the support posts that support the refractory ware are in direct contact with the metal chassis of the kiln car. Secondly, the insulating efficiency needs to be improved by using lower thermal mass kiln car furniture. Thirdly, the posts that support the refractory ware must be placed in a particular fixed relationship to one another because the receiving sockets are part of the kiln car platform. Fourthly, at least a few members of the kiln car furniture must be specifically tooled for the specific dimensions of the kiln car.
Therefore, it is the general object of the present invention to provide hollow load-bearing universal refractory modules for kiln cars that solve these and other problems.